Manufacture of commutators



4 Sheets-Sheet l May 11, 1954 c. A. NICHOLS ETAL MANUFACTURE OFCOMMUTATORS Original Filed Nov. 29, 1947 C. A. NICHOLS ETAL MANUFACTUREOF COMMUTATORS May 11, 1954 4 Sheets-Sheet 2 Original Filed Nov. 29, l

EN TOR I V u u wmw i Zi; Wm yv y 1954 c. A. NICHOLS ETAL MANUFACTURE OFCOMMUTATORS Original Filed Nov. 29, 1947 y 11, 1954 c. A. NICHOLS ET ALMANUFACTURE OF COMMUTATORS 4 Sheets-Sheet 4 Original Filed Nov. 29, 1947Patented May 11, 1954 2,677,874 MANUFACTURE OF COMMUTATORS Charles A.Nichols, Carl L. Clevenger, William A.

Fletcher, and Forest L. Zion,

assignors Anderson, Ind.,

to General Motors Corporation, De-

troit, Mich., a corporation of Delaware Continuation of applicationSerial No.

November 29, 1947.

1950, Serial N0. 176,982

2 Claims. (Cl. 29-155.54)

This application is a continuation of application Serial No. 788,942filed November 29, 1947, now abandoned.

This invention relates to the manufacture of commutators fordynamoelectric machines and, more particularly, to a commutatorcomprising an annulus of metal bars and insulating segments, ringsinsulated from the bars for clamping the bars and a tubular rivet forclamping the rings.

. The object of the invention is to provide a method of manufacturewhich will minimize the possibility of loosening commutator bars. In thedisclosed embodiment of the present invention, this object isaccomplished by the steps of assembling within a ring an annulus of barsand nonconducting segments, each of said bars having initially a tang,forcing the annulus from the assembling ring into a building ring ofsmaller internal diameter whereby the parts of the annulus are squeezedtogether, coining the tangs of the bars while in the second ring intodovetail shape whereby uniform V-grooves are provided, assembling withthe annulus clamping rings, insulation thereof, and a tubular rivethaving, intermediate its ends, a section of reduced thickness, stakingthe rivet to retain the assembly, removing the assembly from thebuilding ring, and forcing welding electrodes against the ends of therivet while applying electric current in order to effect shortening ofthe rivet by hotupsetting of its section of reduced thickness andthereafter discontinuing the electric current and cooling the rivetwhile the electrode pressure is maintained.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

Fig. 1 is a. fragmentary end view looking in the direction of the arrowl of Fig. 2;

Fig. 2 is a sectional view on the line 2-2 of Fig. 1 of a commutatorbuilt by the method of the present invention;

Fig. 3 is a side view of the core or tubular rivet;

Fig. 4 is a plan view of one of the insulating rings;

Figs. 5 and 6 are side and end views respectively of a commutator bar;

Figs. 1 to 6 are drawn to a larger scale than the remaining figures;

Fig. 7 is a longitudinal sectional view of apparatus for transferring anannulus of the comis application August 1,

2 mutator bar insulators from an assembling ring into a building ring;

Fig. 8 is a fragmentary sectional view showing the annulus after beingforced from the assembling ring into the building ring;

Fig. 9 is a longitudinal sectional view of the apparatus for coining thedovetailed tangs of the commutator bars;

Figs. 10 and 10A are showing parts of tions;

views similar to Fig. 9

Fig. 11 is a. longitudinal sectional view of the.

apparatus for removing the assembled commutator from the building ring;

Fig. 16 is a longitudinal sectional view of the I apparatus for hotupsetting the core; and

Fig. 17 is a view similar to Fig. 16 showing the.

condition of the core after being hot upset.

The commutator which is to be built according to the present methodcomprises an annulus of the commutator bars 20 and insulating segments2| clamped together by a tubular rivet or central core 22, the ends ofwhich are formed against V-rings 23 which are insulated from the bars bynon-conducting rings 24. The core 22 is formed preferably from sheetsteel and is pro vided initially with a flange 25 and with an internalannular groove 26 whereby the thickness at section a b is substantiallyless than at other parts of the core. The insulating rings 24 eachprovide a plurality of (preferably four) superimposed washers (Fig. 4)of glass cloth. Fig. 4 is drawn to half the scale of Fig. 2. Theinsulating segments 2| are substantially the same shape as the bars 20as shown in Fig. 5. The tang 21 of each bar 20 is not initially shapedas shown in Fig. 2 but is shaped as shown in Fig. 5.

The required number of bars 20 and insulating.

segments 2| are assembled into an annulus A within an assembling ring 30(Fig. 7). Ring 30 is then placed upon a building ring 3i which rests.

on a support 32. The support 32 rests on a base 33. The support 32encloses a spring 34 urging upwardly a plunger 35 for receiving theannulus A. Plunger 36 moves from the position shown in the apparatus inother posi longitudinal sectional views.

Fig. 7 to that shown in Fig. 8 to force the annulus A from theassembling ring 30 into the building ring 3|.

The building ring 3! containing annulus A is then transferred to theapparatus shown in Figs. 9, 10 and 10A for coining the tangs of thecommutator bars into dovetail tangs. This apparatus comprises a base 4|]adapted to be mounted upon the bed 13 of a press and supporting amandrel 4| urged upwardly by a spring Ma and surrounded by a die 42which receives the flange of the mandrel. The die 42 is attached to thebase 40 by ring 44 secured by screws 45. The base supports posts 45, theupper ends of which extend into sleeves 4? provided by a plate 48attached to the movable head H (Fig. 10) connected with the piston rodor ram R of an hydraulic press. Plate 48 supports an upper die 49secured by a ring 50 attached by screws 5| to the plate 48. A plate 52is supported by the plate 48 by screws 53 threaded in the plate 52, theheads of screws 53 bottoming on shoulders 54 at the bottom ofcounterbores 54a which receive the heads of screws 53. Plate 52 supportsa plate 55 by screws 56 which extend through plate which rest uponsurfaces 51 of the heads of the screws 56. Plate 55 receives screws 48aattached to plate 40. When the press is operated to cause the plate 48to move down, the plate 55, which supports the building ring 3| with theannulu A therein, is caused to descend so that it is supported by die 42as shown in Fig. 10, since the annulus A of commutator bars which engagethe die 42 supports the ring 3 i. As the plate 43 moves down from theposition shown in Fig. 10 to the position shown in Fig. 1 A, the tangs21 of bars 2% are squeezed between the dies 42 and 49 and against themandrel 4i thereby forming the bar tangs, initially shaped (as shown inFig. into dovetail tangs, as shown at .21 in Fig. A.

As their tangs are shaped between the dies '12 and 45, the bars 29 movedown from the position shown in Fig. 10 to that shown in Fig. 10A.During tang formation, the bars 28 are confined by ring 3| so thatoutward movement of metal is prevented. Metal of the bars is permittedto flow inwardly to a limited extent against the mandrel 4| whichconfines the metal to flow along it and into the spaces between the endsof the dies 42 and 49. Thus the inner surfaces of the bar tangs arecaused to conform to the shape of the mandrel and the end surfaces ofthe tangs are caused to conform to the surfaces of the dies. Thus thetangs are accurately shaped to uniform dimensions so that the barsprovide uniform V- grooves 23 (Fig. 2) each defined by a cylindricalsurface 280'. and conical surfaces 28.?) and 28c adapted to receive theinsulating rings 24 and clamping rings 23 which fit the V-grooves 28accurately. Because these V-grooves are each concentric wtih respect tothe mandrel 4!, they are coaxial.

Because the bars are confined between the ring 3| and the mandrel 4!during tang formation, they exert pressure on the ring and mandrel whichincreases as tang formation progresses. Therefore it is necessary thatthe ring 3| and mandrel 4| be permitted to float down with the bars 2|!as they descend from the position shown in 1D to that shown in Fig. 10A.Recess 55a of plate 55 provides clearance for downward floating of ring3 I; and mandrel 4| floats downagainst the action of spring 4m.

During return of the plate 48 from the position shown in Fig. 10A tothat shown in Fig. 9, mandrel H is moved up by spring 4|a until itsflange engages the lower end of die 42. The bars 20 and the ring 3| risewith the mandrel. Since the annulus of bars grip the mandrel 4| withpressure greater than they grip the die 49, the latter is retracted fromthe bars 20. The plate 48 picks up the screws 53 which are attached toplate 52. As plate 52 rises, screws 56 attached thereto pick up theplate 55. As plate 55 rises, it engages the ring 3| and lifts it tostrip the bars 20 from the mandrel.

The building ring 3| carrying the annulus A is transferred to theapparatus shown in Fig. 11, which comprises a plate Gil supported on abed of an hydraulic press and supporting studs 6| surrounded by springs82 which support a plate 63 in an elevated position. Plate 6t supports alower die 54 secured by screws t5. Plate 63 provides a counterbore 65for receiving the ring 3|. Before the ring 3| is placed on the plate 63an insulating ring comprising a plurality of discs 26 is placed upon theplate 53 and around a guide pin 51' located centrally of the die 54 andhaving a flange 68 which rests upon the bed of the press. After the ring3| is placed upon the plate 63 a second ring 24 comprising a plurallityof discs '26 is placed around the pin ill. Then an upper die '58,supported by the ram of the press is caused to descend to force theupper ring 24 into the upper V-groove of the annulus A and to force theannulus against the low-er ring 24 and the latter against the die t l sothat both rings 24 are forced by the dies tit iit into the V-grooves ofthe annulus as shown in Fig. 12. The glass cloth of which each layer oiring it is made, is impregnated with a substance, such that the pressureapplied by the dies causes this substance to be heated slightly that therings retain the shape given to them by the dies and the rings remain inthe V-grooves of the annulus.

The first staking operation is performed by the apparatus shown in Fig.13. This apparatus comprises a base Hi adapted to be supported by thebed of a press and supporting a tube the inner bore of which receivesthe stern l2 of a die 13 secured by a screw 14. The tube "H providesaguide for a stripper block 15 which normally is slightly above the block15 .and is then supported by spring 16 surrounding screws '11 threadedinto the block 15 and having their shanks guided for vertical movementby the base ill and having their heads movable in recesses 18 in base N.The shoulders 19 of the recesses 78 receive the heads of screws I? whenthe springs 16 are permitted to expand. The die 13 cooperates with a die8i supported by a die holder 8| attached to the ram or movable head (notshown) of the press. When the upper die 80 is in its upper position, acore 22 is placed flange end down upon the die 73 and a lower V-ring 23is placed upon said flange. Then the building ring 3| with the annulusA, whose V-grooves have received the insulators 24 as shown in Fig. 12,is placed upon the block 1.5 which has a vcounterbore 82 for receivingthe ring 3|. An upper V-ring 2.3 is placed around the core 22 and withinthe upper V- groove of the annulus. Then the ram 01? the press is causedto descend thereby forcing the .die 8|! against the upper edge of thecore .22 to cause it to flare outwardly as shown in Fig. 13 therebyperforming the first staking operation. Incidentally, the ring 3| movesdown and urges the block 15 toward the base 10 against the action ofsprings 16. When the upper die 80 rises, the

springs 76 expand to raise the block in order to strip the work from thedie 73.

The second staking operation is performed by the apparatus shown in Fig.14 which is similar to Fig. 13, except the lower die 83 and the upperdie 84 are shaped so as to cause the ends of core 22 to be curled aroundthe V-ring as shown best in Fig. Parts in Fig. 14 which are identicalwith those shown in lug. 13 have the same reference numbers with primesaffixed. Although the pressure employed in the second operation isrelatively high, when this pressure is removed, due to the resiliency ofcore 22, the core ends spring back and relieve the pressure upon. the V-rings. The reduced prevent loosening of the bars when the commutator issubjected to high speed of rotation.

The next step is to remove the staked commutator from the building ring3!. The ring is placed upon a C-ring 55 (Fig. 15 )resting upon a support86 and a, plunger 9! is caused to descend to force the commutator fromthe ring 3.! into the opening in the ring $55 which is substantiah lylarger in diameter than the commutator. Next the commutator core 22 ishot upset. This is done by placing the commutator upon a lower electrode90 and an upper electrode 95 is caused to descend upon the core 22 andthe electric current is caused to pass through the core. Since thesection of the core on the line a-b (Fig. 3) is less than the otherportions, the electrical resistance at this section of the core isgreater. Therefore there is a localization of the heat developed by thepassage of electric current and the portion of the core at the groove 26becomes softer than other portions. The application of pressure by theelectrodes while current passes causes a decrease in the length of thecore 22. The groove 26 becomes slightly narrower as in dicated at 26a;and the material which is displaced incidental to the decrease in lengthcauses a bulge or a formation of an annular boss at 261 While theelectrode pressure is still applied the current is turned off andcompressed air is caused to flow from passages 94 in electrode asthrough the core 22 and out through passages 92 in electrode 9|. Thesoftened material at the groove 26a, and the annular boss 2% freezes;and then the electrode 9! is retracted. As the temperature of thecommutator is reduced the core shrinks and its flanges tighten upon theV-rings which apply pressure to the bars and segments sufiicient to holdthem in place against the action of considerable centrifugal force whichexists when the commutator is placed in service.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form,

pressure is insufficient to it is to be understood adopted.

What is claimed is as follows:

1. The method of making a commutator comprising an annulus of metal barsand insulating segments, rings insulated from the bars for clamping thebars and a tubular rivet having a reduced thickness annular centersection for retaining the clamping rings which includes the steps ofproviding an annulus of non-ocnducting segments and metal bars withdove-tail tangs of uniform shape and located in circular alignment thusproviding uniform vgrooves, assembling with the annulus clamping ringsand insulation thereof and a tubular core or rivet, flaring the ends ofthe rivet against the clamping rings to force them firmly into theVgrooves, applying electric current through the rivet for heating saidrivet, simultaneously applying pressure to the ends of the rivetsufficient to hot upset said reduced thickness section of the rivet forshortening the rivet and thereafter, while pressure is maintained,discontinuing the flow of electric current to allow the rivet to coolwhereby contraction of the shortened rivet during cooling substantiallyincreases the pressure exerted by the clamping rings upon the tangs ofthe commutator bars.

2. In the method of making a commutator comprising an annulus ofinsulating segments and metal bars having dove-tail ta-ngs, ringsinsulated from the bars for clamping the tangs and a tubular rivet forclamping the rings, said rivet hav ing intermediate its ends, a sectionof reduced thickness, the steps of forcing welding electrodes againstthe ends of the rivet while applying electric current thereto and thenheating said reduced thickness section by means of said electriccurrent, shortening said rivet by pressure applied by said electrodesfor hot upsetting said section of reduced thickness, thereafterdiscontinuing the electric current and cooling the rivet while theelectrode pressure is maintained.

that other forms might be References Gite-d in the fiie of this patentUNITED STATES PATENTS Number Name Date 1,282,051 Doman Oct. 22, 19181,296,969 Kopsch Mar. 11, 1919 1,587,445 Thomson June 1, 1926 1,676,442Jones July 10, 1928 1,898,696 Sorensen Feb. 21, 1933 2,499,539 SwiftMar. 7, 1950 2,507,780 Gilbert May 16, 1950 2,509,021 Settle May 23,1950 2,516,681 Dolan July 25, 1950

